확장형 칼만필터를 이용한 현수교의 감쇠성능 평가

박동욱(Park Dong-Uk),김남식(Kim Nam-Sik) 대한토목학회 2011 대한토목학회논문집 A Vol.31 No.2A

감쇠비는 현수교에 있어서 교량진동을 평가하기 위한 중요한 동적 요소 중 하나이다. 하지만, 실재 현수교에서 계측된 상시 진동신호로부터 감쇠비를 직접적으로 추정하는 것은 현실적으로 매우 어려운 일이다. 뿐만 아니라, 한정된 계측자료를 이용하여 추정된 감쇠비로부터 공기역학적 감쇠와 마찰 감쇠를 구분하는 것은 더욱 어렵다. Macdonald는 2005년 발표한 자료에서 공기 역학적 감쇠성능은 풍속에 따라 선형적으로 증가한다고 하였으며, Park등은 감쇠성능은 진동의 크기에 따라 변화할 수 있다고 하였다. 따라서 본 논문에서는 이러한 감쇠비, 풍속, 진동의 크기 사이의 관계를 연구하여, 추정 감쇠비로부터 공기역학적 감쇠와 마찰 감쇠를 구분하고자 하였다. 본 논문에서 감쇠비 추정대상으로는 전라남도 고흥에 위치한 소록대교를 선택하였으며, 감쇠비 추정에는 Hilbert 변환법을 이용한 방법과 확장형 칼만필터를 이용하였다. 또한 두 방법으로 추정된 감쇠비들을 상호 비교를 실시하였다. 그 결과, 상시진동 자료와 차량재하실험으로부터 얻어진 자료를 이용하여 추정된 감쇠비와 풍속, 그리고 가속도의 크기를 이용하여 추정 감쇠비로부터 공기역학적 감쇠 성능과 마찰 감쇠 성능의 구분이 가능하다는 것을 알 수 있었다. The damping ratio as an index of bridge vibration could be considered as one of the important dynamic characteristics of a suspension bridge. But estimating of damping ratio on an existing suspension bridge under ambient vibration condition could be a laborious task. Moreover, it is not simple to directly distinguish aerodynamic damping and friction damping from apparent damping. According to previous studies, the aerodynamic damping properties can be linearly affected by wind speed level, and apparent damping ratio can be affected by amplitude of vibration. Therefore, in this article, the relationships among damping ratio, wind speed level and amplitude of acceleration were studied for separating extract aerodynamic damping and friction damping from apparent damping. Damping ratios on Sorok Bridge, a suspension bridge which is a located in Go-Heung, Korea, were estimated by two different methods as using Hilbert transform and extended Kalman filter which were well known as effective estimation methods for non-linear state. It was possible to distinguish aerodynamic damping and friction damping from apparent damping using averaged normal components of wind speed, RMQ values of acceleration, and estimated damping ratios from wind-induced vibration responses and vehicle loading responses.

등속운동을 이용한 관절계 역학적 특성치 정량화 방법의 유용성 평가

이창한(C. H. Lee),허지운(J. U. Heo),김철승(C. S. Kim),엄광문(G.M. Eom) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

The purpose of this study is to evaluate the possibility of identifying joint damping property through commercially available isokinetic ergometer (BIODEX). The proposed method is to estimate the damping torque of the knee joint from the difference between the external joint torque for maintaining isokinetic movement and the gravity torque of the lower leg. The damping torque was estimated at various joint angular velocities, from which the damping property would be derived. Measurement setup was composed of the BIODEX system with an external force sensor and Labview system. Matlab was used in the analysis of the damping property. The experimental result showed that the small variation in angular velocity due to acceleration and deceleration of the crank arm resulted in greater change of inertial torque than the damping torque, so that the estimation of damping property from the isokinetic movement is difficult.

Damping and mechanical properties of composite composed of polyurethane matrix and preplaced aggregates

Lee, Kang Seok,Choi, Jeong-Il,Kim, Sang-Koo,Lee, Bong-Kee,Hwang, Jae-Seung,Lee, Bang Yeon Elsevier 2017 Construction and Building Materials Vol.145 No.-

<P><B>Abstract</B></P> <P>This paper presents an experimental study of the damping and mechanical properties of a new composite produced by a two-stage casting process. Five mixtures according to the materials and manufacturing process were prepared. A series of experiments, including density, impact resonance, compressive strength, flexural strength, and uniaxial tension tests, were performed in order to characterize the damping and mechanical properties of the composite. The test results showed that the composite, which is composed of preplaced aggregate and polyurethane matrix, and produced by manufacturing process proposed in this study, showed significantly improved damping performance as well as better tensile behavior.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two-stage manufacturing process and materials were proposed for high damping property. </LI> <LI> The new composite showed the damping ratio of 18.1%. </LI> <LI> The flexural strength of the composite is higher than that of normal concrete. </LI> <LI> The interfacial property between polyurethane matrix and aggregate was investigated by microscopic observation. </LI> </UL> </P>

Fabrication of carbon nanotubes dispersed woven carbon fiber/epoxy composites and their damping characteristics

Kim, Hee Chul,Kim, Eun Ho,Lee, In,Byun, Joon Hyung,Kim, Byung Sun,Ahn, Seok Min SAGE Publications 2013 Journal of composite materials Vol.47 No.8

<P>Damping characteristics of carbon nanotubes dispersed woven carbon fiber/epoxy composites were investigated. The composites were fabricated by an advanced resin film infusion prepreg manufacturing process based on the calendaring process using three-roll mill. Through this advanced process, well-dispersed nanocomposites containing high weight percent (up to 7 wt%) of carbon nanotubes was achieved. It was confirmed through the scanning electron microscopic images of the carbon nanotubes dispersed composites. Damping characteristics of the specimen were measured by the impact vibration test of the composites beam specimens. Considerable improvement of damping characteristics was observed in the carbon nanotubes dispersed composites, and structural damping increased as the weight percent of carbon nanotubes was increased. Damping ratio was improved up to 12.3% (at the 1st natural frequency) and 16.1% (at the 2nd natural frequency), especially in the 7 wt% carbon nanotubes dispersed specimen. Tensile test was performed to investigate the effects of carbon nanotubes on the tensile properties. The tensile stiffness of carbon nanotubes dispersed composites was similar with the conventional composites; however, tensile strength was degraded.</P>

Mechanical and Damping Properties of Graphene-Modified Polyurethane-Epoxy Composites for Structures

Yi Su,Ting Li,Yanyan Liu 한국고분자학회 2021 폴리머 Vol.45 No.4

Polyurethane (PU) has received extensive attention in structural engineering due to its excellent mechanical properties and damping properties. In this research, graphene-modified PU-epoxy composites are prepared for the application in structural engineering. The mechanical properties and damping properties of the composites with different contents of graphene are investigated. The damping properties of the composites were also investigated by performing dynamic mechanical analysis (DMA). The results showed that with the increase of graphene content, the tear strength of the composites decreased from 52 to 39 ㎫. Due to the enhancement of appropriate amount of graphene, the tensile strength and elongation at break increase to the maximum value, being 16 ㎫ and 675%, respectively. And DMA tests showed that the damping properties reach the optimal values when the graphene content is 0.2%. The large damping temperature range (ΔT0.5) is 33 ℃, from -2.9 to 30.1 ℃. The peak of loss factor (ηmax) is 0.92 and the integral area (TA) is 36 ℃, much higher than those of the pure PU-epoxy composites. In addition, scanning electron microscopy (SEM) results show that agglomeration appears with higher graphene content.

NiAl계 기계적 합금분말의 특성 및 소결합금체의 제진특성

김태규,김유영 진주산업대학교 2001 論文集 Vol.40 No.-

Ni-Al is shape memory alloy in high temperature and is used as high damping material(HIDMET). NiAl alloy powders were prepared by mechanical alloying method and bulk specimens were produced using hot isostatic pressing techniques(HIP). Transformation behavior was investigated by differential scanning calorimeter (DSC), XRD. Particle size distribution and microstructures of mechanically alloyed powders were studied using particle size analyzer and scanning electron microscope (SEM). After 10 hours milling, XRD peak broadening apeared at the alloyed powders with compositions of Ni-36at%Al to 40at%Al. The NiAl and Ni_3Al intermetallic compounds were formed after water quenching of solution-treated powders and bulk samples at 1200℃. It is considered to be caused by fast diffusion of atoms for the formation of stable β(NiAl) phase and Ni_3Al due to nano sized grains during quenching. Amounts of martensite phase increased as the heat treatment times increased in the Ni-Al alloy, which resulted in the increasing damping properties.

Long-term Immersion in Water of Flax-glass Fibre Hybrid Composites: Effect of Stacking Sequence on the Mechanical and Damping Properties

Khouloud Cheour,Mustapha Assarar,Daniel Scida,Rezak Ayad,Xiao-Lu Gong 한국섬유공학회 2020 Fibers and polymers Vol.21 No.1

The hybrid solution of natural-synthetic fibres can be an effective option to enhance the moisture resistance ofnatural fibre reinforced polymer composites. This work aims at studying the effect of long-term water immersion of hybridcomposites on their mechanical and damping properties. These properties were investigated using free vibrations fromsamples composed of quasi-unidirectional flax and glass layers and epoxy resin. The results showed that the saturation massuptake and the diffusion coefficient of the composites were strongly dependent on the stacking sequence between the flax andglass layers. For instance, less than 25 days were necessary to reach the water saturation when flax fibre reinforcements werein the outer layers, whereas it took over 10 months when these reinforcements were in the inner layers. Compared to the flaxfibre reinforced composite, the flax-glass hybrid laminate with two inner flax layers and two outer glass layers was the mostefficient for a specification where damping and bending modulus are the main criteria. This one enabled a significant increasein bending and specific bending moduli (+38 % and +79 % respectively compared to the unaged flax laminate), aconsiderable slowing down of the diffusion phenomenon, while limiting the decrease in damping property with ageing(-20 %).

Stabilization of a Coupled ODE-wave System with Disturbances

Lu Lu,Yu-Long Zhang,Jun-Min Wang,Dong-Xia Zhao 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.3

This paper is devoted to stabilizing an ODE-PDE coupled system with boundary disturbance, where the PDE is chosen to be a wave equation with viscous damping. Applying the active disturbance rejection control (ADRC) technic, the unknown disturbance is estimated by the extended state observer (ESO). Assuming the absence of disturbance, the dynamic boundary connection is designed. The methods of spectral analysis and separation of operator are applied, which ensures the Riesz basis property as well as the spectrum determined growth condition. The exponential stability of the coupled system without disturbance is then concluded. Finally, combining the disturbance estimation and the dynamic boundary connection, a feedback controller designed to stabilize the coupled system, and the closed-loop system is proved to be asymptotically stable.

A stability factor for structure-dependent time integration methods

Shuenn-Yih Chang,Chiu-Li Huang 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.4

Since the first family of structure-dependent methods can simultaneously integrate unconditional stability and explicit formulation in addition to second order accuracy, it is very computationally efficient for solving inertial problems except for adopting auto time-stepping techniques due to no nonlinear iterations. However, an unusual stability property is first found herein since its unconditional stability interval is drastically different for zero and nonzero damping. In fact, instability might occur for solving a damped stiffness hardening system while an accurate result can be obtained for the corresponding undamped stiffness hardening system. A technique of using a stability factor is applied to overcome this difficulty. It can be applied to magnify an unconditional stability interval. After introducing this stability factor, the formulation of this family of structuredependent methods is changed accordingly and thus its numerical properties must be re-evaluated. In summary, a large stability factor can result in a large unconditional stability interval but also lead to a large relative period error. As a consequence, a stability factor must be appropriately chosen to have a desired unconditional stability interval in addition to an acceptable period distortion.

FUTURE APPLICATIONS OF NI-TI ALLOYS IN AUTOMOTIVE SAFETY SYSTEMS

V. GHEORGHITA,P. GÜMPEL,A. CHIRU,J. STRITTMATTER 한국자동차공학회 2014 International journal of automotive technology Vol.15 No.3

The shape memory alloys present unusual thermo-mechanical properties. The most important of them arepseudo-elasticity and memory effect. The paper investigates this behaviour for the Ni-Ti wires under static (v < 50 mm/s) anddynamic conditions (v > 50 mm/s) at different temperatures. Ni-Ti actuator and pseudoelastic wires with diameter between0.1 mm to 0.5 mm are being tested. For dynamic investigation a new testing plant able to satisfy the testing conditions iscreated. This new testing plant is still under development and the reported results originate from the first tests on this newmachine. The new device is designed to reach speeds higher than 50 mm/s. These speeds can be achieved using a drop weightwhich will hit a bottom plate and by this the kinetic energy is transferred to the sample. Because the weight is dropped, thestroke for the sample is measured in two points. The force of this impact will be in-line measured and, if the sample will beelectrically activated during this test, it is also possible to log the electrical voltage. To widen the application range of the shapememory alloys it is necessary to study their behaviour in the dynamic region. With the new testing facility, it is expected totest the damping properties of SMA wires. In that case, these results can generate the basis for finding new applications forshape memory alloys especially in the automotive safety industry.